1. Field of the Invention
The invention relates to a method for foliar fertilization of plants, especially legumes, with ammonium ion and to a novel composition useful therein.
2. Background of the Art
Aqueous fertilizer solutions comprising urea as the source of nitrogen have been extensively utilized for foliar fertilization and have found significant commercial acceptance. However, commercial grades of urea include varying, low concentrations of ammonium ion, and aqueous solutions of commercial urea may decompose at a low pH to generate ammonium ion in situ. It is also well known that ammonium ion, an alternative and cheaper source of fertilizer nitrogen, may cause phytotoxic damage to many plants. Thus, liquid fertilizers do not utilize ammonium ion as a major source of nitrogen and the urea based liquid fertilizers are treated by methods which minimize the ammonium ion content thereof to prevent phytotoxic damage. For example, see U.S. Pat. No. 4,214,888.
In fact, methods of fertilizing conifer forests include utilizing the phytotoxic effect of urea and ammonium nitrate based liquid fertilizer combinations to thin conifer forests so that only the most healthy trees can survive. See for example, U.S. Pat. No. 4,033,746. This reference also mentions that various micronutrients such as iron, molybdenum, manganese, copper, boron, zinc and magnesium may be included as water soluble salts in the aqueous fertilizer solutions disclosed. Since micronutrients by definition function at very low amounts, the amounts included will necessarily be small. Moreover, conifers are not generally found to be as sensitive to the phytotoxicity of ammonium ion as certain other plants, such as legumes. Therefore, the inclusion of magnesium ion in such aqueous fertilizing solutions is for the purpose of providing micronutrients as opposed to reducing the phytotoxic effect of the ammonium ion.
It is well known that many liquid fertilizers which include ammonium ion as a minor nitrogen source can also include micronutrients such as the above mentioned. In U.S. Pat. No. 3,918,952, a composition useful as a liquid fertilizer for lawns is disclosed. However, the concentration of the ammonium ion is not sufficient to cause a phytotoxic reaction of the usual lawn grasses.
Solid fertilizers are known in the art which combine an ammonium ion-containing salt with alkaline earth metal compounds. For example, in U.S. Pat. No. 2,061,534 ammonium chloride is disclosed in combination with magnesium carbonate. There is no teaching that this material is useful as a liquid fertilizer, and there is no suggestion that the amount of magnesium is critical to control the phytotoxicity of the ammonium ion. Moreover, since this material is to be applied as a solid, there will be no danger of the ammonium ion harming the plant during its inevitable slow release into the soil.
It is, therefore, one object of this invention to provide a method for reducing the phytotoxicity of liquid fertilizers comprising ammonium ion.
It is another object to provide ammonium ion-containing foliar fertilizers wherein the phytotoxicity of the ammonium is reduced.
Another object is to provide an ammonium ion-containing liquid fertilizer suitable for use on legumes, such as beans, alfalfa, etc.
Additional objects, advantages and aspects of the invention will become apparent to those skilled in the art from the following disclosure and the appended claims.